Question - In health care facilities is ground fault protection for operation of service and feeder disconnecting means required to be fully selective such that the feeder device but not the service device shall open on ground faults on the load side of the feeder device. Is a six cycle minimum separation between service and feeder ground fault tripping bands required?

First part – Yes, 2 levels of ground fault (service main and branch) are required in a health care facility. This requirement makes sure that the main does not open in the event of a ground fault downstream of a feeder device. This minimizes the disruption to critical circuits in a health care facility.

Second part – Maybe. The 2011 NEC was changed to recognize the fact that newer solid state tripping devices do not require the 6 cycle separation for coordination required by older analog devices. However, the manufacturer and the device trip curves still needs to be consulted in case the tolerances still require that separation for coordination.

New solid state breaker on left. Old ground fault relay on right.

New device ground fault trip curve, narrow band, can be coordinated without 6 cycle separation.

Old device ground fault trip curve, wide band, not as accurate, 6 cycle separation for coordination required